Environmental protection measures increasingly require the avoidance of organic solvents in chemical preparations. Accordingly, aqueous systems are increasingly being employed. In addition, organic solvents are often undesired due to their toxicological properties and their danger of fire.
The preparation of aqueous emulsions of organopolysiloxanes is widely known per se. In EP-A 157,323 (published Oct. 5, 1985, W. Grape et al, Bayer AG), in US-A 4,582,874 (published Apr. 15, 1986, W. Grape et al, Bayer AG), in GB-B 2,085,903 (published June 19, 1985, F. Traver, General Electric Co.) and in U.S. Pat. No. 4,552,910-A to Deubzer et al, aqueous emulsions of organopolysiloxanes are described where the organopolysiloxane, in the liquid state or dissolved in an organic solvent, is emulsified in water with addition of suitable emulsifiers. However, certain problems are encountered when aqueous emulsions are prepared from high-molecular-weight organopolysiloxanes, which are frequently produced in crystalline or at least glassy form, in the absence of organic solvents. In this case, the emulsification step can no longer be carried out using the customary equipment conforming to the state of the art, such as, for example, stand-mounted dissolvers, Turrax units, etc. Canadian Patent 1,205,937 to Traver, describes the preparation of aqueous emulsions of organopolysiloxane resins. The emulsification step is carried out by grinding in a colloid mill, which means that the aqueous system thus obtained must, strictly speaking, be regarded as an organopolysiloxane resin suspension.
Therefore, it is an object of the present invention to provide a process for preparing storage-stable aqueous emulsions from high-molecular-weight organopolysiloxanes which are solid at room temperature without using organic solvents. A further object of the present invention is to provide a process for preparing aqueous emulsions from high-molecular-weight organopolysiloxanes in which the proportion of the individual components and additives can be varied broadly in the emulsions.